With the arm in the same position, the signaler can tell soldiers to freeze in place by making a fist. Formation Signals Formation is the bread and butter of the military, regardless of branch.

Trump gave a speech to attending soldiers commemorating the Army’s 250th anniversary. ... pointing and raising his fist and saying, "thank you very much, thank you." ...

Footage of the IDF's rescue mission shows a soldier give former hostage Almog Meir Jan a fist bump, with the video used on the Wikipedia entry for 'fist bumps.' ...

Once soldiers are attacked, the bullets might come flying from more than just other ground infantry. A whole subset of signals comes into play for attacks of different kinds, and from other fronts.